1. Technical Field
The inventive arrangements relate generally to methods and apparatus providing advanced operating features for audio only, video only and both video and audio programs recorded on disc media, for example recordable digital video discs, hard drives and magneto optical discs.
2. Description of the Related Art
Various devices have been developed to enable consumers to record video and/or audio programs for later presentation. Such devices include tape recorders, video cassette recorders, recordable compact discs, and most recently, recordable digital video discs (DVD). Hard drives and magneto optical discs have also been used.
A DVD that can be recorded on only once, and thereafter is essentially a DVD read only memory, is referred to by the acronym DVD-R. The acronym DVD-R is also used generally to refer to the write-once, or record-once, technology. Several formats are available for DVD""s to be recorded on, erased and re-recorded; that is, overwritten or rewritten. These are referred to by the acronyms DVD-RAM, DVDxe2x88x92RW and DVD+RW. As of this time no uniform industry standard has been adopted. The acronyms DVD-RAM, DVDxe2x88x92RW and DVD+RW are also used generally to refer to the respective rewritable technologies. Reference herein to rewritable DVD technology, devices and methods is generally intended to encompass all of the standards which are now being used, as well as those which may be developed in the future.
In many cases, the program presentations are recorded in the viewer and/or listener""s absence, for presentation at a later, more convenient time. This is referred to as time shifting the program. At other times, a program is being viewed and/or listened to without being recorded, and with out any interest in a recording, but the viewer""s and/or listener""s attention is interrupted, for example by a telephone call or an unexpected visitor. If the viewer and/or listener is watching a television program, for example, and has a cassette tape in a VCR, or can retrieve and load such a cassette tape quickly, the program can be recorded. However, the viewer and/or listener cannot view and/or listen to the program in its entirety, and in a proper time sequence, until after the recording has been completed. The time to completion of the recording can be short or long, depending on the length of the program.
Although rewritable DVD technology is generally available, operation is limited to such basic functions as play, record, fast forward reverse and stop. Pause is available, but only as a counterpart to pause operation in a VCR, for example interrupting the play back of a prerecorded program or interrupting the recording of a viewed program to eliminate commercials from the recording. Unlike computer hard drives, recordable DVD devices have a very significant additional function, which is playing back prerecorded DVD""s. Thus, there is an economic incentive to develop rewritable DVD technology, including methods and devices, that can be used instead of a computer hard drive. It is a challenge to provide such devices with improved, advantageous features without compromising the goal of decreasing costs and increasing sales.
It is desirable for any recordable DVD device to have some editing features. Consumers demand such features in order to make their own home videos for special events such as weddings, birthday parties and so on. Such features are also useful after recording a TV program. For example, a consumer may wish to erase commercials from certain programs, for example sports events and movies.
In an MPEG bit stream, the smallest access unit is a group of pictures or GOP. In DVD the smallest access unit is a VOBU. Each VOBU is nominally comprised of a group of pictures (GOP). As such, normal MPEG editing only edits to a GOP without decoding and re-encoding the MPEG encoded signal at a picture level. Thus, most editors today are functionally limited in terms of resolution to a minimum of GOP editing, which is around 0.5 second resolution. In these types of conventional systems, users cannot arbitrarily define beginning and ending points at a picture level of resolution for the purpose of marking bit-stream segments upon which editing operations are to be performed. In any case, the result is that an edit may be displaced as much as 0.5 seconds from the beginning and ending points selected by a user.
In general, the foregoing limitation is attributable to the complexity associated with decoding and re-encoding the DVD video data to the level of a single picture. DVD video is highly compressed in order to make maximum use of available disc space. The compression technique most commonly used essentially involves storing a single picture in full detail and subsequently storing only changes associated with subsequent images. The technique uses three kinds of pictures which are commonly referred to as Intra pictures (I pictures), Predicted pictures (P pictures) and Bidirectional pictures (B pictures). I pictures are reference pictures in which the entire picture content is compressed and stored. I pictures are treated as reference pictures from which other pictures can be assembled. I pictures can be directly accessed within a video stream as they contain all of the data needed to reproduce the picture. By comparison, P pictures cannot independently be used to reproduce a picture. Instead, such pictures contain motion vectors which describe differences from the closest previous I picture or P picture. Finally, B pictures are encoded by looking forward and backward to the next I or P picture to match macroblocks forming these I and P pictures.
The following is a typical GOP structure of 15-picture GOP in display order without detelecine: B0 B1 I2 B3 B4 P5 B6 B7 P8 B9 B10 P11 B12 B13 P14. However, other GOP structures are possible and can be used as well. Regardless of the precise GOP structure used, B pictures cannot be randomly accessed as such pictures cannot be properly decoded without the surrounding I pictures and P pictures. Similarly, the P pictures cannot be properly decoded without reference to the most immediately preceding I picture within the bit stream. This difficulty creates special problems for implementing editing functions in recordable DVD as it means that certain pictures within the bit stream cannot practically be separated from the surrounding pictures.
A method is disclosed for editing to a picture a group of pictures (GOP) in a DVD media without decoding and encoding of an MPEG encoded signal including the steps of: marking a user selected end picture to identify a selected segment of the encoded signal to be edited; automatically identifying an actual end picture for the selected segment based on a position of the user selected end picture relative to at least one other picture within the encoded signal; and performing an edit function on an actual segment delimited by the actual end picture.
The identifying step with respect to the actual end picture is includes assigning the actual end picture to be at least one of an I picture and a P picture most nearly adjacent to the user selected picture if the user selected end picture is not at least one of an I picture and a P picture. The method can also include the step fo blanking the actual end picture and deleting any B pictures appearing between the user selected end picture and the actual end picture. According to one aspect the step of identifying the actual end picture includes assigning the actual end picture to be the user selected end picture if the user selected end picture is an I picture or a P picture.
The method can further include the steps of marking a user selected start picture to identify a selected segment of the encoded signal to be edited; and automatically identifying an actual start picture for the selected segment based on a position of the user selected start picture relative to at least one other picture within the encoded signal. The identifying step with respect to the start picture can include assigning the actual start picture to be an I picture most immediately preceding the user selected picture if the user selected picture is a B picture or P picture. Further, the method can include the step of deleting any B pictures appearing between the user selected picture and the actual start picture. In this regard, the method can also include the step of blanking any I picture and any P picture appearing between the user selected picture and the actual start picture.
According to one aspect, the identifying step with respect to the actual start picture can include assigning the actual start picture to be the user selected start picture if the user selected start picture is an I picture. According to another aspect, the identifying step with respect to the actual start picture can include assigning the actual start picture to be an I picture in a subsequent GOP if the user selected picture is within about the last two pictures of a GOP containing the selected picture.
In an alternative embodiment, the invention can include a rewritable DVD device for editing to a picture a group of pictures (GOP) in a DVD media without decoding and encoding of an MPEG encoded signal. The device is responsive to a user input for marking a user selected end picture to identify a selected segment of the encoded signal to be edited; automatically identifies an actual end picture for the selected segment based on a position of the user selected end picture relative to at least one other picture within the encoded signal; and provides editing functions for performing an edit function on an actual segment delimited by the actual end picture.
The rewritable DVD device defines the actual end picture to be at least one of an I picture and a P picture most nearly adjacent to the user selected picture if the user selected end picture is not at least one of an I picture and a P picture. The device can blank the actual end picture and deletes any B pictures appearing between the user selected end picture and the actual end picture. The system can also define the actual end picture to be the user selected end picture if the user selected end picture is an I picture or a P picture.
The device can also be responsive to a user input for marking a user selected start picture to identify a selected segment of the encoded signal to be edited; and can automatically identify an actual start picture for the selected segment based on a position of the user selected start picture relative to at least one other picture within the encoded signal. The device defines the actual start picture to be an I picture most immediately preceding the user selected picture if the user selected picture is a B picture or P picture. The device can also delete any B pictures appearing between the user selected picture and the actual start picture. The device can also blank any I picture and any P picture appearing between the user selected picture and the actual start picture.
According to one aspect, the rewritable DVD device identifies the actual start to be the user selected start picture if the user selected start picture is an I picture. Alternatively, the rewritable DVD device can identify the actual start picture to be an I picture in a subsequent GOP if the user selected picture is within about the last two pictures of a GOP containing the selected picture.